WO2017126533A1

WO2017126533A1 - Gas collection method

Info

Publication number: WO2017126533A1
Application number: PCT/JP2017/001500
Authority: WO
Inventors: 千春青山; 大樹青山
Original assignee: 千春青山
Priority date: 2016-01-21
Filing date: 2017-01-18
Publication date: 2017-07-27
Also published as: AU2017210423B2; US20210206659A1; JP2017128950A; EP3428384A1; CN108699900A; EP3428384A4; RU2698338C1; US11370672B2; EP3428384B1; AU2017210423A1; KR20180102178A

Abstract

A gas collection method for collecting gas produced from a raw material (PL) present in a seabed (L1) or lakebed, wherein: [1] a collection film (11) is dropped into the water, fixing tools (31) being connected to the lower end of the collection film (11), and the collection film (11) comprising a film body expanding downward from a top part (T1); [2] the three-dimensional positions of the fixing tools (31) in the water are perceived by position-maintaining tools (31) provided to the fixing tools (31), and the three-dimensional positions of the fixing tools (31) are maintained at the desired positions by autonomous navigation; [3] on the basis of the water temperature distribution in the vertical direction acquired by a CTD, the lower end of the collection film (11) is set to a position that is higher than the seabed (L1) or lakebed and shallower than the water depth at which the raw material (PL) separates from a solid state into water and gas, and the top part (T1) of the collection film (11) is set to a position deeper than the water depth at which gas mixes with the seawater or lake water and gas bubbles disappear; and [4] gas released from the seabed (L1) or lakebed is collected by the collection film (11).

Description

Gas collection method

The present invention relates to a gas collecting method that collects a gas such as methane gas emitted from the sea bottom (hereinafter also including a lake bottom).

Recently, attempts have been made to collect gases released from various gas hydrates such as methane hydrate existing under the seabed. The gas hydrate buried under the seabed is divided into water and gas according to conditions such as temperature and atmospheric pressure, and the separated gas rises toward the sea surface. When gas rises to the sea level, it may be mixed with seawater and mixed with seawater. Therefore, in order to collect the gas separated from the gas hydrate, it is necessary to collect the gas before it is mixed with seawater.

The following Patent Document 1 discloses a method for recovering seabed resources. In the method disclosed in Patent Document 1, crude oil ejected from the seabed is collected by a dome-shaped frame, and is collected by a crude oil recovery ship on the sea surface via a pipe connected to the frame.

Japanese Unexamined Patent Publication No. 2012-21357

However, since the purpose of the method disclosed in Patent Document 1 is to recover crude oil, it is necessary to sink the dome-shaped frame and fix it stably. For this reason, the anchor which divides | segments a circular area | region in the seabed is installed, and there exists a possibility of affecting marine fishery resources, such as a shrimp and a crab.

An object of the present invention is to provide a gas collection method capable of efficiently collecting gas released from the seabed (lake bottom) without affecting marine resources on the seabed (lake bottom).

A feature of the present invention is a gas collection method for collecting a gas generated from a raw material existing on the seabed or lake bottom, which comprises a film body having a fixture connected to the lower end and extending downward from the top. The film collecting is dropped into water, the three-dimensional position of the fixture in the water is grasped by a position maintainer provided in the fixture, and the three-dimensional position of the fixture is determined by autonomous navigation. The lower end of the trapping membrane is higher than the seabed or the lake bottom, and the raw material is separated from a solid state into water and gas based on the vertical water temperature distribution obtained by CTD. And set the top portion of the trapping membrane at a position deeper than the water depth at which the gas bubbles are lost when the gas is mixed with seawater or lake water, and the seabed or the lake bottom. More released The collecting in the collection layer, to provide a gas collecting method.

According to the above feature, the lower end of the collection membrane is set at a position higher than the seabed (lake bottom) and shallower than the water depth at which the raw material separates into water and gas from the solid state. Can be collected. Furthermore, it is possible to prevent the fishery resources on the seabed (lake bottom) from being affected.

FIG. 1 is an explanatory diagram illustrating a basic configuration [fundamental configuration] of a gas collection device that performs a gas collection method. FIG. 2 is a graph showing the relationship between seawater temperature and water depth at which methane hydrate is separated into water and methane. FIG. 3 is a perspective view of the gas collecting device. Drawing 4 is an explanatory view showing the composition of the gas collection device which performs the gas collection method concerning an embodiment. FIG. 5 is a flowchart showing a collection procedure using the gas collection device. FIG. 6 is an explanatory view showing a configuration of a modified example of the gas collection device.

Hereinafter, embodiments will be described with reference to the drawings.

[Basic configuration]
First, prior to the embodiment, a basic configuration of a gas collection device that performs a gas collection method will be described. As shown in FIG. 1, the gas collecting device 10 is subtracted from a ship 21 floating on the sea toward the sea bottom (lake bottom) L1, and spreads downward [flare (s) downward] collecting membrane [collecting membrane] ] 11. That is, the collection film 11 is formed of a film body that spreads downward from the top T1. The distance from the lower end of the collection film | membrane 11 to the top part T1 is 100 m, for example. The collection film 11 is supported by four wires 12. A weight 13 fixed to the seabed L1 is connected to each lower end of the wire 12. That is, the weight 13 is attached to the lower end of the collection film 11 and functions as a fixture for maintaining (fixing) the collection film 11 at a desired water depth.

When the weight 13 sinks to the sea bottom L1 so that the weights 13 attached to the lower ends of the wires 12 are located at the corners of the rectangular region, the trapping film 11 supported by the wire 12 has the top T1 at the highest point. As a quadrangular pyramid. There are four gas plumes [gas 粒 plume (s)] PL formed by releasing gas and gas hydrate (raw material) grains (for example, methane gas and hydrate particles) from the seabed L1. When the pyramid-shaped collection film 11 is sunk, the gas and gas hydrate released from the sea bottom can be collected by the collection film 11. Hereinafter, methane hydrate will be described as an example of gas hydrate, and methane gas will be described as an example of gas to be collected.

One end of a tube 14 (for example, a double spiral tube) is connected to the top T1 (or the vicinity thereof) of the collection film 11. The other end of the tube 14 is connected to an onboard unit 22 provided on the ship 21. That is, the methane gas collected by the collection film 11 is supplied to the shipboard unit 22 via the tube 14.

The onboard unit 22 includes equipment such as a gas-liquid separator 30 connected to the tube 14 and a pressure accumulating tank 32 that accumulates recovered methane. The onboard unit 22 takes out the methane gas from the methane gas collected via the tube 14 and the gas-liquid mixture collected along with the methane gas, and sends the methane gas to downstream equipment. For example, the extracted methane gas is sent to a gas storage tank via a pipeline.

The trapping film 11 is made of a material that can withstand long-term use without being stretched or deteriorated even when placed in seawater for a long time.

The lower end of the collecting film 11 is separated from the seabed L1 (see distance P1 in FIG. 1). That is, the weight 13 is sunk on the seabed L1, but the lower end of the collection film 11 is disposed at a position (shallow position) higher than the seabed L1. Moreover, the top part T1 of the collection film | membrane 11 is arrange | positioned in the position deeper than the water depth which methane gas mixes with seawater and a bubble lose | disappears. With this configuration, the methane gas can be collected in a state where the methane hydrate (raw material) is separated into water and methane gas. Furthermore, even when methane gas is mixed with seawater, methane gas can be collected before it is completely mixed.

Here, the water depth at which methane hydrate (raw material) separates into water and gas and the water depth at which the bubbles of methane gas disappear vary depending on the seawater temperature. Hereinafter, the relationship between the water depth at which methane hydrate is separated into water and gas and the seawater temperature will be described with reference to FIG.

The horizontal axis of the graph shown in FIG. 2 indicates the seawater temperature (° C.), and the vertical axis indicates the depth (m) from the sea surface. The + mark indicated by the reference sign Q1 indicates the seawater temperature and water depth at which methane hydrate (solid) is separated into water and gas, which is obtained by calculation. Therefore, the (approximate) curve (Q1) obtained from the + mark indicated by the reference sign Q1 is a methane hydrate stable region curve [methane hydrate stability zone curve]. On the left side of this curve Q1, methane hydrate exists as a solid. On the right side of curve Q1, methane hydrate separates into water and methane gas. Therefore, as can be seen from the curve Q1, the lower the seawater temperature, the shallower the water depth that exists as methane hydrate (solid). For example, at a water depth of 500 m, when the water temperature exceeds 5 ° C., methane hydrate is separated into water and gas. At a water depth of 300 m, when the water temperature exceeds 2 ° C., the methane hydrate is separated into water and gas.

A curve Q2 shown in FIG. 2 shows a typical water temperature change in the sea area of Japan. As can be seen from the curve Q2, the water temperature rises rapidly when the water depth is shallower than 300 m. That is, based on the correspondence between the curve Q2 of the target sea area (here, the Japan Sea area) and the methane hydrate stable area curve Q1, the water depth at which methane gas disappears can be obtained. In the example shown in FIG. 2, it can be seen that methane gas is generated from methane hydrate in the vicinity of a water depth of 300 m. Therefore, if the collection film 11 is installed so that the lower end of the collection film 11 is at a position shallower than the water depth of 300 m, methane gas generated from methane hydrate can be collected.

Furthermore, when the water depth at the lower end of the collection film 11 is shallower, methane gas is mixed with seawater, so that methane gas cannot be collected efficiently. Therefore, it is preferable to arrange the lower end of the collection membrane 11 at the water depth near the intersection of the curve Q1 and the curve Q2.

Next, a procedure for collecting methane gas from the methane plume PL discharged from the seabed L1 using the gas collecting device 10 described above will be described. First, when the presence of the methane plume PL from which the methane gas is released from the seabed L1 is confirmed and the methane gas contained in the methane plume PL is collected, the ship 21 is moved to the sea level above the methane plume PL. Next, the weight 13 is sunk on the seabed, and the weight 13 is moved to a desired position using a robot operating in the sea. Specifically, the weight 13 is moved by remote control by the robot so that the methane plume PL is positioned at the approximate center of the spread collection film 11. Various robots that operate in the sea are known, and detailed description of the configuration and operation of the robot is omitted.

A wire 12 is connected to the weight 13, and a collecting film 11 is attached to the wire 12. Accordingly, the trapping film 11 spreads downward in a quadrangular pyramid shape from the top T1 (see FIG. 3). Here, the collection film 11 was expanded in a quadrangular pyramid shape using four weights 13. However, the collection film 11 may be spread in a polygonal pyramid shape using three or five or more weights 13. Moreover, although it is preferable that the shape of the extended collection film | membrane 11 is a polygonal cone shape or a cone-shaped cone shape, it is not limited to these shapes. The collection film 11 only needs to be expanded in a shape that expands downward and has the top portion T1 as the uppermost point.

The lower end of the collection film 11 is arranged at a position higher than the seabed L1. Therefore, as indicated by the distance P1 (see FIG. 1), a gap is formed between the seabed L1 and the lower end of the trapping film 11, so that the influence on marine resources that inhabit the seabed can be reduced.

Also, the top portion T1 of the collection membrane 11 is disposed at a position deeper than the water depth at which methane gas is mixed with seawater and cannot be confirmed by acoustic sonar. Methane gas separated from methane hydrate is mixed with seawater while ascending about 100 to 200 m and cannot be confirmed with acoustic sonar.

However, here, the top T1 of the collection film 11 is disposed at a position deeper than the water depth at which methane gas is mixed with seawater and cannot be confirmed by acoustic sonar. For this reason, methane gas can be collected by the collection film | membrane 11 before mixing with seawater. The collected methane gas is introduced into the tube 14 connected to the top portion T <b> 1 of the collection film 11, and supplied to the onboard unit 22 provided on the ship 21. The supplied methane gas is separated by the gas-liquid separator 30 and stored in the pressure accumulation tank 32.

Thus, in the gas collection device 10 having the basic configuration, the methane gas is collected by the collection film 11 spreading downward, so that the methane gas generated from the methane plume PL can be collected efficiently.

Moreover, since the lower end of the collection film 11 is disposed at a position higher (shallow) than the seabed L1, it is possible to prevent the marine resources of the seabed L1 from being affected. Furthermore, since the lower end of the collection film 11 is disposed at a position shallower than the water depth at which the methane hydrate is separated into water and methane gas, the methane gas can be collected efficiently.

Furthermore, in the gas collection device 10 having the basic configuration, unlike the method of collecting using a conventional drilling rig, methane gas generated from the methane plume PL is collected. Can be moved. Moreover, since the movement is easy, it is possible to easily collect methane gas released from the surface layer type methane hydrate.

[Embodiment]
Next, the gas collection method (gas collection device 50) according to the embodiment will be described. In the basic configuration described above, the weight 13 is sunk to the seabed L 1, and the collection film 11 is spread by the wire 12 connected to the weight 13. In the present embodiment, the end of the wire 12 is connected to a non-cable type (non-cable type) underwater robot 31 that functions as a weight. The underwater robot 31 is placed at a desired depth in the sea, and the collection film 11 is spread through the wire 12. That is, the underwater robot 31 functions as a fixture for maintaining the collection film 11 at a desired water depth. Furthermore, the underwater robot 31 also functions as a position maintainer for maintaining the position of the fixture.

As shown in FIG. 4, the gas collection device 50 in the present embodiment includes a collection film 11 that hangs down from the ship 21 floating on the sea toward the sea bottom L1 and spreads downward. In other words, the collection film 11 has a configuration including a film body that spreads downward from the top T1. The trapping film 11 is supported by four wires 12, and an underwater robot 31 for holding at a desired position in the sea is connected to the lower end of each wire 12.

One end side of the tube 14 is connected to the top portion T <b> 1 of the collecting film 11, and the other end side of the tube 14 is connected to an onboard unit 22 provided on the ship 21. That is, the methane gas collected by the collection film 11 is supplied to the onboard unit 22 via the tube 14.

The underwater robot 31 has a function of grasping its own position, and can navigate in the direction of 360 degrees autonomously. That is, if the coordinates of the target position are set, the underwater robot 31 recognizes the target position by the above function, autonomously navigates to the target position, and maintains the target position. Therefore, even if a force acts from the lateral direction of the collection film 11 due to the influence of the tidal current or the like, the underwater robot 31 autonomously navigates against the tidal current and maintains the target position. Therefore, the trapping film 11 can be maintained at a desired position without causing the weight 13 to sink to the seabed L1 as in the basic configuration described above.

Next, a procedure for collecting methane gas from the methane plume PL discharged from the seabed L1 using the gas collecting device 50 described above will be described (see FIG. 5). When the presence of the methane plume PL is confirmed and methane gas contained in the methane plume PL is collected, the ship 21 is moved to the sea level above the methane plume PL. Next, after dropping the underwater robot 31 into the sea (step S10) and grasping the position of the underwater robot 31 (step S20), the underwater robot 31 is moved to the target position (step S50). Specifically, the underwater robot 31 is moved so that the methane plume PL is positioned at the approximate center of the spread collection film 11. The position of the underwater robot 31 can be grasped by radio or sonar.

Further, the wire 12 is connected to the underwater robot 31, and the collecting film 11 is attached to the wire 12. Accordingly, the trapping film 11 spreads downward in a quadrangular pyramid shape from the top portion T1 (see FIG. 4). When the target position of the underwater robot 31 is determined (step S40), the underwater robot 31 is made to recognize the coordinates of the target position. The acquisition of the water temperature distribution (step S30) and the determination of the target position based on the water temperature distribution (step S40) will be described later. The target position may be set in advance before the underwater robot 31 is dropped into the sea, or may be set wirelessly. Since the underwater robot 31 performs autonomous navigation so as to remain at the target position, the trapping film 11 can stably collect methane gas from the methane plume PL (step S60).

As in the basic configuration described above, the metagas of the methane plume released from the seabed L1 is collected by the collection film 11 and collected by the tube 14. The advantages of the basic configuration described above are also brought about in this embodiment. Further, in the present embodiment, the use of the underwater robot 31 capable of autonomous navigation instead of the weight 13 provides further advantages.

In the gas collection device 50 in the present embodiment, the underwater robot 31 is connected to the end of the wire 12, and the collection film 11 is maintained at a desired target position by autonomous navigation of the underwater robot 31. Therefore, it is not necessary to sink the weight 13 to the sea bottom L1 as in the basic configuration, and the collection film 11 can be installed at a desired depth even when the water depth of the sea bottom L1 is deep. As a result, methane gas can be reliably collected without being affected by the topography of the seabed L1.

Moreover, since the lower end of the collection film 11 is disposed at a position (shallow) higher than the depth at which the solid methane hydrate is separated into water and methane gas, the methane gas can be collected efficiently.

However, in the present embodiment, the top portion T1 of the collection film 11 is disposed at a position deeper than the water depth at which methane gas is mixed with seawater and cannot be confirmed by acoustic sonar. For this reason, methane gas can be collected by the collection film | membrane 11 before mixing with seawater. The collected methane gas is introduced into the tube 14 connected to the top portion T <b> 1 of the collection film 11, and supplied to the onboard unit 22 provided on the ship 21. The supplied methane gas is separated by the gas-liquid separator 30 and stored in the pressure accumulation tank 32.

In this embodiment, the underwater robot 31 is connected to each end of the wire 12. However, a weight can be connected together with the underwater robot 31 in order to obtain a desired weight.

[Modification]
Next, a modification of the above embodiment will be described. In the above embodiment, the trapping film 11 is maintained at a desired target position by autonomous navigation of the unreasonable underwater robot 31. On the other hand, in this modified example, the trapping film 11 is maintained at a desired target position by the underwater [cable type] ([tethered]) underwater robot 41. Hereinafter, a modified example will be described in detail with reference to FIG.

As shown in FIG. 6, the gas collection device 51 according to the present modification, as in the above embodiment, is a collection that hangs down from the ship 21 floating on the sea toward the sea bottom (lake bottom) L1 and spreads downward. A membrane 11 is provided. That is, the collection film 11 is formed of a film body that spreads downward from the top T1. The collection film 11 is supported by four wires 12. A cabled underwater robot 41 for maintaining the collecting film 11 at a desired position in the sea is connected to each lower end of the wire 12.

A plurality of support vessels 42 for maintaining the position of each underwater robot 41 in the sea floats on the sea surface. Each support ship 42 is connected to the underwater robot 41 by a support wire 43. In FIG. 6, only two sets of the underwater robot 41 and the support ship 42 are shown, but the collection film 11 is expanded by the four sets of the underwater robot 41 and the support ship 42.

Each support ship 42 has a function of grasping its own position, and can recognize the position (latitude / longitude) of the underwater robot 41 based on the relative positional relationship with the underwater robot 41. Therefore, the underwater robot 41 can be maintained at a desired target position by controlling the position of the support ship 42 even if the underwater robot 41 itself does not have an autonomous navigation function or a function of grasping its own position. The target position may be set in advance before dropping the underwater robot 41 into the sea, may be set wirelessly, or may be set by wire via the support wire 43. Also, the position of the underwater robot 31 can be grasped by wire, wireless or sonar.

In the gas collecting device 51 in the modified example, a roped underwater robot 41 is connected to the end of the wire 12, and the underwater robot 41 is connected to the support ship 42. The underwater robot 41 is moved by the navigation of the support ship 42 to maintain the collection film 11 at a desired target position. Therefore, it is not necessary to sink the weight 13 to the sea bottom L1 as in the basic configuration, and the collection film 11 can be installed at a desired depth even when the water depth of the sea bottom L1 is deep. As a result, methane gas can be reliably collected without being affected by the topography of the seabed L1. In addition, since the underwater robot 41 is connected to the support ship 42 by the support wire 43, it is not necessary for the underwater robot 41 to have an autonomous navigation function. Therefore, the configuration of the underwater robot 41 can be simplified, and the apparatus scale can be reduced.

Regarding the determination of the target position described above (step S40), the water temperature distribution in the vertical direction of the sea area is acquired in advance using a measuring device 23 such as CTD (Conductivity Temperature Depth profiler) (step S30). The water depth at the target position of the collection membrane 11 is determined based on the water depth at the intersection of the curve Q2 in the middle) and the methane hydrate stable region curve (see the curve Q1 in FIG. 2). Further, the horizontal coordinate of the target position of the collection film 11 is determined in consideration of the position (path) of the methane plume PL. That is, the lower end of the collection film 11 is set at a position higher than the seabed and shallower than the water depth at which methane hydrate is separated into water and gas, and the top T1 of the collection film 11 is filled with seawater. The position of the collection film 11 that is set at a position deeper than the water depth at which the bubbles disappear is mixed as the target position (step S40).

The gas collection method of the present invention is not limited to the above embodiment (and its modifications). The configuration of each part can be replaced with any configuration having the same function.

For example, in the above embodiment, methane gas released from methane hydrate existing under the seabed (including the lake bottom as described above) is collected. However, the present invention can also be applied to collecting gas hydrates other than methane hydrate, for example, gas released from ethane hydrate or butane hydrate.

Further, the acquisition of the water temperature distribution (step S30) may be performed before the determination of the target position (step S40). Further, the determination of the target position (step S40) may be performed before the underwater robot 31 (41) is dropped into the sea, or may be performed after the drop. However, the determination of the target position (step S40) must be performed before maintaining (moving) the underwater robot 31 (41) at the target position (step S50).

Claims

A gas collection method for collecting gas generated from raw materials existing on the seabed or lake bottom,
A trapping membrane consisting of a membrane body, which has a fixture connected to the lower end and spreads downward from the top, is dropped into water,
By grasping the three-dimensional position of the fixture in the water by a position maintainer provided in the fixture, maintaining the three-dimensional position of the fixture at a target position by autonomous navigation,
Based on the vertical water temperature distribution obtained by CTD, the lower end of the collection membrane is higher than the sea bottom or the lake bottom, and more than the water depth at which the raw material is separated into water and gas from a solid state. While setting to a shallow position, the top of the collection membrane is set to a position deeper than the water depth where the gas is mixed with seawater or lake water and the gas bubbles disappear,
A gas collection method for collecting gas released from the seabed or the lake bottom with the collection film.
The gas collection method according to claim 1,
The raw material is methane hydrate,
Obtain a methane hydrate stable region curve indicating the relationship between the water depth and water temperature at which the methane hydrate separates into water and gas,
The gas collection method of setting the water depth near the intersection of the water temperature distribution and the methane hydrate stable region curve as the position of the lower end of the collection membrane.